1. Field of the Invention
This invention pertains to a pushbutton electrical switch assembly having a multipart housing that includes a slidably retained pushbutton, a lighting system, an actuation member and switching members, in the form of microswitches, wherein via the actuation of the pushbutton, the actuation member is displaced against a resilient force and acts upon the switching members.
2. Discussion of the Background of the Invention and Material Information
U.S. Pat. No. 4,504,713 discloses a modularly built pushbutton electrical switch assembly having an optical display that signals the switching state. The pushbutton electrical switch assembly is comprised of a housing module, a housing cover module, a contact carrier module and a lamp module. The lamp module, comprised of a lamp holder and a lamp, is contained in the housing module. The contact carrier module is slidably retained in the housing module, wherein the housing module utilizes fixed contacts whereas the contact carrier module utilizes resilient contacts. A pushbutton, slidably retained in the housing cover module, upon actuation, moves the contact carrier module against a resilient force up to a stop, whereby contact is established between the fixed and the resilient contacts. The pushbutton is comprised of translucent material so that the illumination of the lamp, which extends through an aperture in the contact carrier module, can be observed at contact making. The housing module and the housing cover module include superimposed bosses, including apertures, for receiving threaded bolts, the latter being welded to an indicator board, for example for elevators, with these bolts serving for the attachment of the pushbutton switch.
A disadvantage of this pushbutton electrical switch assembly resides in the relatively high or great installation depth, particularly due to the lamp module, so that this switch cannot be utilized in those installations that only have a small space between the indicator board and the wall or another boundary limit. The high depth is, on one side, due to the elongated form of the filament bulbs which, moreover, only have a short service life and are sensitive to vibrations so that they must be replaced quite often, which is both time-consuming and expensive. On the other hand, the installation depth is also necessitated by the relatively complicated and expensively assembled lamp holder which includes handles that extend out of the switch housing during bulb changing.
European Patent Publication EP-A-0 548 556 discloses a command and indicator apparatus that utilizes a multipart pushbutton having a displaceable lighting system. The latter is comprised of light-emitting semiconductors, arranged on a first printed circuit board, whose light is channeled, via an annular light pipe or cable, to the underside of a glass that forms the front side of the pushbutton. The light pipe runs along the edge of the glass, with the uncovered area of the glass being covered with an opaque layer, so that, during actuation of the pushbutton, a light ring appears as an acknowledgement signal. The pushbutton is slidably retained in a spherical indentation which is connected with a switch carrier via a snap connection. A second printed circuit board is attached at the lower end of the switch carrier, with a microswitch being carried by the circuit board. The actuation of a pot-shaped plunger of the pushbutton actuates the switching element of the microswitch.
The microswitch is arranged in such a manner that the switching element is displaced in the direction of movement of the pushbutton. Moreover, since the lighting apparatus, the plunger and the microswitch are located behind each other in the direction of movement of the pushbutton, a relatively great installation depth results therefrom. Additional disadvantages are present in that two printed circuit boards are required which have to be connected with flexible multi-conductor leads and plug contacts whereby the assembly becomes more complicated and more expensive. In addition, via the use of the previously described, as well as with a point-shaped light source variation of the lighting system, no uniform full illumination of the pushbutton can be achieved.